Apple on Monday updated a pair of support documents relating to the release of macOS Mojave, outlining legacy Mac Pro compatibility via graphics card upgrades and support for Boot Camp on certain iMac models.

A first document walks users through installing macOS Mojave on the Mid 2010 and Mid 2012 Mac Pros. As mentioned previously, these machines did not ship with GPUs that support Metal -- Apple's 3D graphics API -- and must be updated before upgrading to macOS Mojave.

Apple lists a series of GPUs that support Metal, and thereby macOS Mojave, for those looking to keep their aging workhorses up to date.

The following cards are known to be Metal-compatible:

MSI Gaming Radeon RX 560 128-bit 4GB GDRR5

SAPPHIRE Radeon PULSE RX 580 8GB GDDR5

SAPPHIRE Radeon HD 7950 Mac Edition

NVIDIA Quadro K5000 for Mac

NVIDIA GeForce GTX 680 Mac Edition

Apple also lists cards that "might also be compatible" with macOS Mojave:

AMD Radeon RX 560

AMD Radeon RX 570

AMD Radeon RX 580

AMD Radeon Pro WX 7100

AMD Radeon RX Vega 56

AMD Radeon RX Vega 64

AMD Radeon Pro WX 9100

AMD Radeon Frontier Edition

To check which graphics card is currently installed in a given Mac, press and hold the Option key and navigate to Apple menu > System Information > Graphics/Displays. Compatible cards will show "Supported" next to the Metal entry.

A second support document helps resolve the "Installation cannot proceed with Boot Camp configured" alert that might show up on certain iMac models when attempting to install macOS Mojave.

This alert appears only on 27-inch iMacs from late 2012 with 3TB hard drives installed and an existing Boot Camp partition. To bypass the message, users must back up their Windows data, then remove the Boot Camp partition before installing Mojave.

Apple warns users that after they do perform the removal, they will no longer be able to use Boot Camp to install Windows on their machine.

I know of too many people who have Macs because they took a chance, but having Windows available to use was what won them over.

Not very Apple-like as far as non-solutions go.

This alert appears only on 27-inch iMacs from late 2012 with 3TB hard drives installed and an existing Boot Camp partition.

I am pretty sure this only happen on 2012 27" iMac model with 3TB hard drive installed and an existing Boot Camp partition. Pretty specific, not even a minor cases. So not exactly as you claimed that it happened on most Macs. I am pretty sure none of the "many people you know who have Macs" have that particular model with that particular HDD. It could be that particular model hardware no longer supported it. You still can install windows with Parallel if required.
note: 6 years old iMac has no business to install Mojave.

Oh, did you hear that, everybody? An Internet schmoe has decided what you should do with your own property, and that you've gotten enough value from your investment.

Hey, guess what? Even Windows 10 has restrictions on what hardware it will run on. What exactly are you trying to say here? How far back in time does an operating system have to support your “investment”?

AI made an editorial blunder with a confusing headline that some have interpreted as saying ALL iMacs will no longer support Boot Camp. Turns out it’s a specific configuration accompanied by the engineering reasons. But no, it’s all an evil planned obsolescence conspiracy theory by an evil corporate entity known as Apple. How much longer do we have to endure this nonsense? It’s getting really old.

AI made an editorial blunder with a confusing headline that some have interpreted as saying ALL iMacs will no longer support Boot Camp. Turns out it’s a specific configuration accompanied by the engineering reasons.

I personally would love it if Apple provided built-in support for later nVidia graphics cards, but I know that is unlikely because all of the current off the shelf options use AMD graphics solutions. I have seen claims on some of the forums that people with GT 710 and GT 730 cards (Kepler architecture, same as GTX 680) have gotten those cards to work with Metal under Mojave. I do not own these cards to test these claims, but if correct these cards would provide a low cost Mojave upgrade path for those not doing graphics intensive tasks with their cheese grater Mac Pro towers.